通过IP地址，获取MAC地址，好像只能适用于局域网

public class ClassNetGetMac
 {
  public ClassNetGetMac()
  {
  }

  [DllImport("Iphlpapi.dll")]
  private static extern int SendARP(Int32 dest,Int32 host,byte[] mac,ref Int32 length);
  [DllImport("Ws2_32.dll")] 
  private static extern Int32 inet_addr(string ip);

  ///

  /// 根据ip得到网卡mac地址
  ///

  /// 给出的ip地址
  /// 对应ip的网卡mac地址
  public static string GetMACByIP(string ip) 
  { 
   try 
   { 
    byte[] aa=new byte[6];

    Int32 ldest= inet_addr(ip); //目的地的ip

    Int64 macinfo = new Int64(); 
    Int32 len = 6; 
    int res = SendARP(ldest,0, aa, ref len);

    return BitConverter.ToString( aa, 0, 6 );;
   } 
   catch(Exception err) 
   { 
    throw err; 
   }
  }

 }